We will continue to apply immunocytochemical procedures for the localization of the gonadotrophic hormones, FSH and LH in sections of rat anterior pituitary glands. This will involve the use of antisera to subunits of those hormones. In another study, tritiated N-acetyl neuraminic acid will be injected into ovariectomized rats in order to label newly synthesized FSH; the labeled hormone will then be localized by light and electron microscopic radioautography. We anticipate that this procedure will differentially label newly synthesized FSH molecules. The main thrust of the proposal will be directed towards a detailed study of the ultrastructure of prolactin cells in rat pituitary autografts. Quantitative morphometric methods will be applied to the cell organelles involved in hormone secretion and the results will be correlated with the prolactin levels in the autografts and in the blood of the animals as measured by radioimmunoassay. The role of the pineal gland and the hypothalamus in modifying prolactin secretion will be examined in appropriate animal groups. A major objective of this proposal will be to establish a pure clonal line of prolactin cells. This will be done by the use of cells from pituitary autografts which demonstrate the greatest enrichment of prolactin cells having normal ultrastructural morphology.